Interactions of alpha and beta synuclein proteins in auditory functioning

Alpha-synuclein is found in synaptic terminals at the base of both inner and outer hair cells, while the beta isoform is prominently localized to spiral ganglion neuron cell bodies. The present study assessed the role of beta-synuclein in auditory function, and potential interactions between isoforms.

Emotional interactions and an ethic of care: caring relations in families affected by HIV and AIDS

In the context of global processes of economic restructuring, the HIV and AIDS epidemic and socio-cultural constructions of care, many women and young people in low-income households have been drawn into caring roles within the family. Drawing on the literature on an ethics of care, emotional geographies and embodiment, this paper examines the emotional dynamics of the caring process in families affected by HIV and AIDS. Based on the perspectives of both ‘caregivers’ and ‘care-receivers’ from research undertaken in Namibia, Tanzania and the UK, we examine the everyday practices of care that women and young people are engaged in and explore how emotions are performed and managed in caring relationships. Our research suggests caregivers play a crucial role in providing emotional support and reassurance to people with HIV, which in turn often affects caregivers' emotional and physical wellbeing. Within environments where emotional expression is restricted and HIV is heavily stigmatised, caregivers and care-receivers seek to regulate their emotions in order to protect family members from the emotional impacts of a chronic, life-limiting illness. However, whilst caregiving and receiving may lead to close emotional connections and a high level of responsiveness, the intensity of intimate caring relationships, isolation and lack of access to adequate resources can cause tensions and contradictory feelings that may be difficult to manage. These conflicts can severely constrain carers' ability to provide the ‘good care’ that integrates the key ethical phases in Tronto's (1993) ideal of the caring process.

Rational modification of the hierarchy of intermolecular interactions in molecular crystal structures by using tunable halogen bonds

A family of 16 isomolecular salts (3-XpyH)(2)[MX'(4)] (3-XpyH=3-halopyridinium; M=Co, Zn; X=(F), Cl, Br, (I); X'=Cl, Br, I) each containing rigid organic cations and tetrahedral halometallate anions has been prepared and characterized by X-ray single crystal and/or powder diffraction. Their crystal structures reflect the competition and cooperation between non-covalent interactions: N-H center dot center dot center dot X'-M hydrogen bonds, C-X center dot center dot center dot X'-M halogen bonds and pi-pi stacking. The latter are essentially unchanged in strength across the series, but both halogen bonds and hydrogen bonds are modified in strength upon changing the halogens involved. Changing the organic halogen (X) from F to I strengthens the C-X center dot center dot center dot X'-M halogen bonds, whereas an analogous change of the inorganic halogen (X') weakens both halogen bonds and N-H center dot center dot center dot X'-M hydrogen bonds. By so tuning the strength of the putative halogen bonds from repulsive to weak to moderately strong attractive interactions, the hierarchy of the interactions has been modified rationally leading to systematic changes in crystal packing. Three classes of crystal structure are obtained. In type A (C-F center dot center dot center dot X'-M) halogen bonds are absent. The structure is directed by N-H center dot center dot center dot X'-M hydrogen bonds and pi-stacking interactions. In type B structures, involving small organic halogens (X) and large inorganic halogens (X'), long (weak) C-X center dot center dot center dot X'-M interactions are observed with type I halogen-halogen interaction geometries (C-X center dot center dot center dot X' approximate to X center dot center dot center dot X'-M approximate to 155 degrees), but hydrogen bonds still dominate. Thus, minor but quite significant perturbations from the type A structure arise. In type C, involving larger organic halogens (X) and smaller inorganic halogens (X'), stronger halogen bonds are formed with a type II halogen-halogen interaction geometry (C-X center dot center dot center dot X' approximate to 180 degrees; X center dot center dot center dot X'-M approximate to 110 degrees) that is electrostatically attractive. The halogen bonds play a major role alongside hydrogen bonds in directing the type C structures, which as a result are quite different from type A and B.

Tissue culture propagation alters plant-microbe interactions in tobacco rhizosphere

We have compared properties of roots from different lines (genotypes) of tobacco raised either in tissue culture or grown from seed. The different lines included unmodified plants and plants modified to express reduced activity of the enzyme cinnamoyl-CoA reductase, which has a pivotal role in lignin biosynthesis. The size and structure of the rhizosphere microbial community, characterized by adenosine triphosphate and phospholipid fatty acid analyses, were related to root chemistry (specifically the soluble carbohydrate concentration) and decomposition rate of the roots. The root material from unmodified plants decomposed faster following tissue culture compared with seed culture, and the faster decomposing material had significantly higher soluble carbohydrate concentrations. These observations are linked to the larger microbial biomass and greater diversity of the rhizosphere communities of tissue culture propagated plants.

Microbial impacts on plant-herbivore interactions: the indirect effects of a birch pathogen on a birch aphid

The role of indirect interactions in structuring communities is becoming increasingly recognised. Plant fungi can bring about changes in plant chemistry which may affect insect herbivores that share the same plant, and hence the two may interact indirectly. This study investigated the indirect effects of a fungal pathogen (Marssonina betulae) of silver birch (Betula pendula) on an aphid (Euceraphis betulae), and the processes underpinning the interaction. There was a strong positive association between natural populations of the aphid and leaves bearing high fungal infection. In choice tests, significantly more aphids settled on leaves inoculated with the fungus than on asymptomatic leaves. Individual aphids reared on inoculated leaves were heavier, possessed longer hind tibiae and displayed enhanced embryo development compared with aphids reared on asymptomatic leaves; population growth rate was also positively correlated with fungal infection when groups of aphids were reared on inoculated branches. Changes in leaf chemistry were associated with fungal infection with inoculated leaves containing higher concentrations of free-amino acids. This may reflect a plant-initiated response to fungal attack in which free amino acids from the degradation of mesophyll cells are translocated out of infected leaves via the phloem. These changes in plant chemistry are similar to those occurring during leaf senescence, and are proposed as the mechanistic basis for the positive interaction between the fungus and aphid.

Indicators of nitrate in wetland surface and soil-waters: interactions of vegetation and environmental factors

This paper describes a new bio-indicator method for assessing wetland ecosystem health: as such, the study is particularly relevant to current legislation such as the EU Water Framework Directive, which provides a baseline of the current status Of Surface waters. Seven wetland sites were monitored across northern Britain, with model construction data for predicting, eco-hydroloplical relationships collected from five sites during 1999, Two new sites and one repeat site were monitored during 2000 to provide model test data. The main growing season for the vegetation, and hence the sampling period, was May-August during both years. Seasonal mean concentrations of nitrate (NO3-) in surface and soil water samples during 1999 ranged from 0.01 to 14.07 mg N 1(-1), with a mean value of 1.01 mg N 1(-1). During 2000, concentrations ranged from trace level (<0.01 m- N 1(-1)) to 9.43 mg N 1(-1), with a mean of 2.73 mg N 1(.)(-1) Surface and soil-water nitrate concentrations did not influence plant species composition significantly across representative tall herb fen and mire communities. Predictive relationships were found between nitrate concentrations and structural characteristics of the wetland vegetation, and a model was developed which predicted nitrate concentrations from measures of plant diversity, canopy structure and density of reproductive structures. Two further models, which predicted stem density and density of reproductive structures respectively, utilised nitrate concentration as one of the independent predictor variables. Where appropriate, the models were tested using data collected during 2000. This approach is complementary to species-based monitoring, representing a useful and simple too] to assess ecological status in target wetland systems and has potential for bio-indication purposes.

Interactions between earthworms and arsenic in the soil environment: a review

Chemical pollution of the environment has become a major source of concern. In particular, many studies have investigated the impact of pollution on biota in the environment. Studies on metalliferous contaminated mine spoil wastes have shown that some soil organisms have the capability to become resistant to metal/metalloid toxicity. Earthworms are known to inhabit arsenic-rich metalliferous soils and, due to their intimate contact with the soil, in both the solid and aqueous phases, are likely to accumulate contaminants present in mine spoil. Earthworms that inhabit metalliferous contaminated soils must have developed mechanisms of resistance to the toxins found in these soils. The mechanisms of resistance are not fully understood; they may involve physiological adaptation (acclimation) or be genetic. This review discusses the relationships between earthworms and arsenic-rich mine spoil wastes, looking critically at resistance and possible mechanisms of resistance, in relation to soil edaphic factors and possible trophic transfer routes. (C) 2003 Elsevier Science Ltd. All rights reserved.